What is Battle Smith?

Battle Smith is a subclass for the UA artificer.

If you had find steed, and this cast on it, if the steed were attacked, thus both of you receive damage, could you then react with shield, which would affect both of you potentially nullifying all damage to you both?

Quote from belfastbiker >>

If you had find steed, and this cast on it, if the steed were attacked, thus both of you receive damage, could you then react with shield, which would affect both of you potentially nullifying all damage to you both?

 Shield is a reaction spell that can be cast when you are hit with an attack, not when you take damage.

Absorb Elements, though...

Also thought of a bearbarian/cleric build that capitalizes on this spell not needing concentration. Your partner gains resistance to everything, and then you resist your share of his/her damage.

This spell is awesome when you cast it on yourself. One hour of +1 AC and saving throws? With no concentration? Epic.

'Also, each time it takes damage, you take the same amount of damage'. If I have resistance that damage type, my resistance applied?

Quote from TheRavenOfDarkness >>

This spell is awesome when you cast it on yourself. One hour of +1 AC and saving throws? With no concentration? Epic.

 Wait, you can cast it on yourself???

How does the part about taking the same damage when the target gets damage work? Is it double the damage, or does it only do damage once?

With anything, I believe that you can determine however you would like to use the spell, but the wording and intent of the spell appears to require two creatures to be involved Casting creature and target. 
It doesn't expressly say you cannot cast it on yourself but it also mentions a bond between two separate beings, Casting and target. 
There is also mention of a * platinum ring worth 50gp, with each separate person wearing it; substitute for something of like value(?).
I don't know how you can be a Ward to yourself and gain a benefit, it simply doesn't make sense and I would assume it to not be the intent of the spell.

Ward (verb):
ARCHAIC
guard; protect.
"it was his duty to ward the king"

So, if a Battle Smith casts this on a Barbarian who is already raging, the Barbarian will still be damaged for the same amount, since resistance sources don't stack.  This is essentially a way to protect your tank.  The spell also says the damage soak is a one-way street; your spell's target will not absorb damage from you.

You would take half of the attack’s damage initially, due to resistance, then you would be hit for that amount of damage, again taking only half, then you’re hit again, ad Infinitum.  In theory, this would eventually approach the initial damage.  However, rounding would mean it’s at least 1 less than the original hit, sometimes less than that.  For instance, if you were hit for 15, you would take 7+3+1=11 damage total.

How would this work with twinned spell?

A clever use. I was brainstorming ideas myself as well. But depending on the DM it might not work. For the spell requires both targets to wear a platinum ring worth 50gp

Arguably could be an platinum earring

Wich a horse could have? But that's up to DM digression

Quote from Sniperwes20 >>

How would this work with twinned spell?

 Technically, it wouldn't.  Officially, you can only Twin a spell that can magically affect a single creature, but it magically affects at least two: Your target, and Yourself.

Thoughts on what type of monster might have the “materials” necessary to craft (downtime) a magical item imbued with this spell in it?

You cant target yourself, you must fulfill the entire spell requirements of the spell by targeting another creature.

so who takes the damage?  Does this mean that the damage that was intended for the attacked willing creature get's transferred to the Caster?

Am I correct in understanding that each of the bonded creatures take 1/2 of the reduced damage received? Or if a bonded created receives 12pts damage, halved to 6 then each character takes 6pts damage?

Grrrr. Why is this not available to an Oath of Redemption paladin? This would be perfect for that Oath - soaking up damage intended for others like so many other features of that Oath.

It is now available to paladins through Tasha's extended spell lists.  Up to the DM if they will allow it though.

It is not showing up on the list of spells that I can select and the detail page does not list Paladin as an eligible class (but Oath of the Crown is eligible). Am I missing something or do I need to figure out how to report a potential problem?

nvm - I found the setting buried in the character editor to turn it on.